The excellent rms of the data permits detection of emission up to \(V_{\rm LSR}\approx \)  \(-20\hbox{\hspace{1.99997pt}km\hspace{1.99997pt}s$^{-1}$}\)  in the different transitions of HCN.
Several transitions of DCN, H\(^{13}\) CN and HC\(^{15}\) N were also detected towards L1157-B1 and their profiles display similar broad linewidths, confirming the shock association (Fig. REF ). The detection of bright deuterated emission suggests that despite shock processing, the gas has preserved part of the initial chemical conditions, an effect already pointed out by [1]} and [2]}, who reported the detection of singly deuterated isotopologues of H\(_2\) CO, CH\(_3\) OH, NH\(_3\) . A small systematic velocity shift (less than \(0.5\hbox{\hspace{1.99997pt}km\hspace{1.99997pt}s$^{-1}$}\) ) is measured between the emission peaks of the HCN and HNC line profiles, suggesting they are tracing different regions inside the shock.
